CVD with “Ancient Text” Clouds

jewellery magazine

The Surat lab received a 1.67 ct D-color pear shape submitted for laboratory-grown diamond service. Spectroscopy and fluorescence imaging confirmed this was a diamond grown by chemical vapor deposition (CVD) that had undergone post-growth high-pressure, high-temperature (HPHT) annealing. This CVD diamond with SI1 clarity displayed an interesting cloud feature that resembled lines of text in an ancient manuscript (figure 1).

Figure 2. A DiamondView image of the pavilion shows the region containing the cloud characteristic. While this image reveals the growth interfaces and the coloration confirms HPHT annealing, it does not show features corresponding to the cloud. Image by Suvarna Gaikwad.

The “lines” of clouds—a feature never before seen by the authors—were oriented approximately 45° to the growth interface seen with DiamondView imaging (figure 2). Examination of the fluorescence images (including those collected with selective-wavelength filters) revealed that the cloud features did not coincide with dislocation bundles, and striations were not observed. Photoluminescence mapping with 532 nm excitation showed high concentrations of the silicon vacancy (SiV) defect at 737 nm but did not indicate any spatial features corresponding to the clouds. Infrared absorption spectroscopy indicated a type IIb diamond with very low concentrations of uncompensated boron.This diamond was noteworthy for its unusual and visually appealing clarity characteristic. Additionally, the dichotomy of a thoroughly modern diamond with a cloud feature that evoked an ancient text provided an interesting submission.


This article is reproduced with permission from GIA

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